1. Field of the Invention
The present invention relates generally to the field of image data processing, and, more particularly, the present invention relates to an improved method for processing decoded picture blocks.
2. Description of the Related Art
In known systems, if video data is compressed by coding methods based on transformation codings, errors in certain picture areas inevitably occur. For example, the use of the discrete cosine transformation for motion pictures at an extremely low transmission rate of approximately 8 to 112 kbit/s, such as that used with mobile radio telephone applications and video phone applications results in picture errors.
The picture errors manifest themselves in artificial edges of block borders and noise or other fuzziness. These coding errors have a disturbing effect for the viewer and distort the overall picture image. Artificial edges at block borders are a problem which occurs with all block-based coding methods. These artificial edges significantly reduce the image quality for the viewer. Other undesirable effects also appear in motion picture errors of a picture sequence which is referred to as video data current.
U.S. Pat. No. 5,367,629 describes a method wherein decoded picture blocks are stored and the picture block edge pixels are filtered with an edge-smoothing filter. One disadvantage of this method is that for each picture block, the same edge-smoothing filter is used and block-border filtering adapted to the characteristics of the picture block is not possible. This results in degradation of the picture quality during reproduction which is less desirable than that which is capable of being achieved with the present invention.
U.S. Pat. No. 4,754,492 discloses alternate methods for block-based picture-coding methods. The methods disclosed in this reference similarly fail to produce the improvements in image quality which are capable of being achieved through the present invention.